Rate Law and Reaction Rate Calculator
Calculate reaction rate using rate = k[A]^m[B]^n.
Find how doubling a concentration affects rate for 0th, 1st, and 2nd order reactions.
The rate law expresses how reaction rate depends on the concentration of reactants.
General rate law:
rate = k × [A]^m × [B]^n
Where:
- k = rate constant (units depend on overall order)
- [A], [B] = molar concentrations (mol/L)
- m, n = individual reaction orders (experimentally determined, usually 0, 1, or 2)
- Overall order = m + n
Effect of doubling a concentration:
| Order | Rate changes by |
|---|---|
| 0 | No change (rate = k) |
| 1 | Doubles (2¹ = 2×) |
| 2 | Quadruples (2² = 4×) |
Units of rate constant k:
| Overall order | Units of k |
|---|---|
| 0 | mol L⁻¹ s⁻¹ |
| 1 | s⁻¹ |
| 2 | L mol⁻¹ s⁻¹ |
| 3 | L² mol⁻² s⁻¹ |
Determining reaction order experimentally: Use the method of initial rates: compare how rate changes as concentration changes.
If doubling [A] doubles the rate → first order in A. If doubling [A] quadruples the rate → second order in A. If doubling [A] has no effect → zero order in A.
Example: For 2NO(g) + O₂(g) → 2NO₂(g): Rate = k[NO]²[O₂] — second order in NO, first order in O₂, third order overall. At [NO] = 0.01 M, [O₂] = 0.01 M, k = 7×10⁹ L²/mol²/s: Rate = 7×10⁹ × (0.01)² × (0.01) = 7×10³ mol/L/s
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